NB3SN SUPERCONDUCTORS PREPARED FROM INTERMEDIATE COMPOUND PHASE

Nb3Sn tape with upper critical field B-c2 of approximate to 25 T at 4. 2 K has been prepared by a new process using intermediate Nb6Sn5, comp ound powder. B-c2 is still increased by a small amount of Ti doping. T he pre-reaction between Nb6Sn5 and Nb powders, caused by mechanical mi xing, promotes the synthesis of A15 Nb3Sn in the subsequent heat treat ment. The fabrication of tape specimens using a Ta sheath has been eas ily performed. The critical current density of Nb3Sn exceeds 3.3 x 10( 4) A Cm-2 at 20 T and 4.2 K. Present Nb,Sn specimens exhibit considera bly larger normal state resistivity than bronze-processed Nb3Sn, which may enhance B-c2 in the specimens.